Embolization of post-partial nephrectomy upper calyceal-perirenal urinary fistula using onyx-34: A novel application of a (pseudo-) liquid embolic agent

ABSTRACT Persistent urinary fistulas are a clinically significant complication of nephron-sparing renal surgery, and surgical revisions are difficult procedures with risks, especially in frail patients with relevant comorbidities. We report the first documented case of successful urinary fistula closure using Onyx-34, a nonadhesive liquid embolic agent. A patient with pheochromocytoma, sigmoid adenocarcinoma, and left renal mass developed a persistent urinary leak refractory to conservative treatment. Due to the high risk of surgical revision, the fistulous tract was embolized with Onyx-34 through a percutaneous nephrostomy access, achieving immediate complete clinical resolution of the leak. This case highlights the potential of Onyx-34 as a minimally invasive option for managing complex urinary fistulas in selected patients.